Fuel cells implement an electrochemical redox reaction while simultaneously producing electricity. For this purpose, the electrodes of the cell need to be fed respectively with a fuel, generally hydrogen, and with an oxidizer, namely oxygen (e.g. taken from a stream of air introduced into the core of the cell).
Hot fuel cells, e.g. such as fuel cells of the solid oxide fuel cell (SOFC) type, operate at very high temperatures (about 900° C.). That makes it possible, in particular, for them to be used advantageously in so-called “cogeneration” systems, i.e. systems that generate both heat energy and electrical energy. Such cogeneration systems may be used equally well in industrial applications and in home applications (e.g. producing heat and electricity in individual houses).
In such systems, the fuel cell needs to be associated with a device such as a boiler or a heat exchanger, which device is capable of recovering the heat from the gas exhausted from the cell. Unfortunately, the gas coming from a hot fuel cell is at very high temperature, thereby making it impossible, downstream from the hot fuel cell, to make use of standard boiler systems designed for processing heat flows at lower temperatures.
Typically, most boilers are made of low-performance materials, such as stainless steel, thereby enabling heat to be exchanged at lower cost between a hot stream and a cooling fluid. Nevertheless, it is very difficult to control the injection and the flow of very high-temperature gases in boiler circuits made of such materials.
One solution to that problem might consist in using high-performance materials that are good at withstanding flows at high temperature. However, the use of such materials would considerably increase the cost of the cogeneration system, which is undesirable, in particular for home applications.